The present disclosure relates to a method for determination of molecules. More particularly, the present invention relates to a method for determination of molecules by means of an aptamer.
Biosensors consist of a material capable of discriminating molecules and a transducer to detect physical and/or chemical signals arising from mutual actions between the material and a target chemical substance. Among conventional materials capable of discriminating molecules are proteins such as enzymes, antibodies, and receptors.
Document 1 (BUNSEKI KAGAKU Vol. 51, No. 6, (2002) 389-396) discloses a method for high-speed screening of endocrine disrupting chemicals by means of a surface plasmon resonance (SPR) sensor. This method consists of immobilizing the hormone responsive sequence DNA (ERE) of the promoter region of the estrogen responsive gene on an SPR sensor chip and adding a purified estrogen receptor α (ER) to it, thereby measuring the mutual action of ER and ERE in real time without modification.
Unfortunately, proteins are unsuitable for long-term use because they are limited in life on account of their chemical and thermal instability and they are subject to nonspecific adsorption.
What is attracting attention as a substitute for proteins is an aptamer, which is a nucleic acid sequence that brings about a specific binding like an antibody for antigens ranging from low-molecular weight compounds to proteins. Being not a protein, an aptamer has an advantage in stability and life. Moreover, it is expected to find use as a biosensor because of its ability for reproduction under comparatively mild conditions, its potential for economical mass production by chemical synthesis, and its property characteristic of nucleic acids, such as reversible binding with and dissociation from complementary strands.
Document 2 (J. Am. Chem. Soc. 128, (2006) 3138-3139) discloses an electrochemical method for observing the change that occurs in the structure of an aptamer on account of the presence of cocaine as a target substance when the terminal of an aptamer is modified with methylene blue.